Due to the development of computer graphics (CG) technologies, it has become possible to represent a virtual space (also called "virtual world") that is set up in virtual fashion three-dimensionally and in real time. This is the technical field of video games machines: these have been developed in recent years and incorporate a central processing unit (CPU) capable of high speed computation and a video display processor (VDP) and enable such computer graphics technologies to be utilised at high speed and in economical fashion.
In such a video games machine, the content of game play changes continually depending on the actions of the user (also called the game player or player), so the objects that are displayed have to be moved freely at high speed in virtual space. To this end, usually a model constituting an object to be displayed (for example a character) is constituted of a set of polygonal fragments called polygons of triangular or quadrilateral shape, and the movement of such models is displayed by simultaneously altering the spatial position of these polygons.
Also, when specified portions or faces of objects to be displayed such as the arms or legs of characters were to be moved simultaneously, a polygon data group consisting of an assembly of a plurality of polygons was taken as a unit and a spatial position was given to each polygon data group, so that the specified portions or faces could be moved simultaneously.
In recent years, so-called 3D (three-dimensional) games have attracted attention in the market, in which a character is made up of polygons and an image is represented on a monitor in which the movement of the character in virtual space is captured from a virtual viewpoint; simulations of fights between a plurality of warriors are particularly popular (for example, "Virtual Fighter" (trade mark) made by Sega Enterprises Limited). In such a fighting simulation game, a player rapidly operates a stick or pad or button attached to a controller to make a warrior represented on the screen perform actions in accordance with commands determined by operation of the stick etc. The movements of the warrior are called "motion" and data in order to implement such motion is acquired using the "motion capture" technique. This data is then processed, if need be, and is utilised as final motion data in a 3D video games machine. In such a video game, in order to raise the product value, it is desirable to represent the movement of the character more realistically. More specifically, this consists in for example adding more varieties of movement whilst approaching very closely to the actions of an actual warrior. However, since the anticipated movements of a character extend over a very wide range of possibilities, there are many problems that still need improvement in order to achieve such an objective. Of course, consideration has been given to for example compiling beforehand all the desired motion data and storing this in memory and obtaining characteristic expressions in order to get such motion, but the problem is that a large amount of data is required for this, which is impossible to process in real time.
A chief object of the present invention is therefore to provide an image processing technique for games whereby the amount of calculation and/or the amount of data required for image processing can be greatly reduced and whereby the movement of the character on the screen can be expressed more in real time and more realistically.
First specific aspects of a problem that was experienced in conventional video games machines from the point of view of this object are as follows.
A1. In a 3D video game, since the image on the two-dimensional screen from the virtual viewpoint is represented by performing a projection conversion, it is difficult to move the warrior in the depth direction of the screen (z direction of virtual space) i.e. in the direction of the player's gaze, so no consideration at all was given to enabling a warrior to walk around other warriors. To improve such movement around the characters is therefore a first specific object of the present invention.
A2. With a conventional 3D video games machine, there was the problem that, since the images were displayed from a virtual viewpoint, if a structure such as a wall was arranged in virtual space in a position such as to screen the warrior, display was effected with the character blocked out. Accordingly, a further specific object of the present invention is to effect display in which this situation that the character is blocked out by a structure is improved.
A3. In a conventional video games machine, the method was adopted of generating the motion of the character sequentially using for example a spline function, or the method of effecting reproduction of predetermined patterns in sequential frames. However, with the conventional video games machine, this motion was fixed, so it was not possible to correct the motion to match the movement of a character on the other side etc. Accordingly, a further specific object of the present invention is to enable such motion correction to be performed.
Further, as a derivation from the viewpoint of the above chief object, in addition to the first aspects described above, it is desired to perform screen display with improved dramatic effect such as character movement, in order to raise product value. Second aspects of the problems of conventional video games machines when this demand is taken into consideration may be described specifically as follows.
B1. "Motion blur" is known as a technique for improving the dramatic effect of a CG image. By means of such motion blur, a large number of rays are generated at a single pixel, and coloration is applied wherein these are averaged, thereby enabling a picture to be created that shows "out-of focus" or movement. Furthermore, in recent years, in the field of CG video such as video games, in order to raise the dramatic effect further, in movement of a character, display is effected together with residual images such as are liable to be produced physiologically in human visual perception. For example, residual images may be attached to the track of a sword that is being waved by a warrior. Persons skilled in the art would therefore calculate polygons and to constitute residual images matching the motion of the warrior and display these residual images in the vicinity of the warrior.
However, the anticipated movements of characters are extremely diverse, so compiling polygons for a large number of modes of residual images matching all these cases and storing these in memory restricts the performance of a limited computer graphics device and furthermore calculation of residual-image polygons in conformity with the motion of the character puts a large load on the computer graphics device. Accordingly, in the formation of a CG image, yet a further specific object of the present invention is to make it possible to display residual images simultaneously with the actual image screen without large increase in calculation load (or more precisely, reducing the load), even though measures are taken to raise the dramatic effect.
B2. In a games device using a conventional image processing device, flying material such as sand or water splashes is displayed on the screen (for example "Sega Rally" (trade mark) manufactured by Sega Enterprises Limited). However, since such water splashes or sand scattering consisted merely in mapping texture on to polygons, it was not possible to reflect accurately the movement of the model (car etc.) by the flying material. Yet a further specific object of the present invention is therefore to reflect the movement of the model more accurately in the flying material.
B3. The quality of the conventional image processing device was insufficient in simulation of movement of a model falling in virtual space. Yet a further specific object of the present invention is therefore to raise the quality of simulation of movement of free-fall through virtual space.
B4. In a conventional image processing device, the proximity of a zone in virtual space and a moving model were determined and if this determination was positive, movement of. the model was restricted such as not to go beyond the zone. Usually, as zones of this type, fixed-shape, for example quadrilateral or circular, type zones were set up. In this case, since the zone was of a typical shape, it was easy to calculate movement that would expel the character from the zone. However, when this zone was irregularly shaped, there was the problem that it was difficult to cope with this situation with the conventional computer graphics device. Accordingly, yet a further specific object of the present invention is to enable the calculation processing of the movement (motion) of a model after there has been a positive determination of collision between the zone and the model to be executed accurately and easily.
B5. Conventionally, in the field of image processing applied in games devices, when a series of periodic pictures (for example, a picture of repeating waves or skipping etc.) was to be reproduced, a series of such pictures was compiled by a manual operation to produce a texture series and a series of images in which the same action was repeated were represented by repeated sequential mapping of these on to a polygon.
Since the compilation of such texture series requires a lot of manual work, attempts have been made to utilise application software. A known example of such application software is called by the trade name: Alias/Wavefront (manufactured by Alias/Wavefront Inc. (110 Richmond Street, East Toronto, Ontario, Canada, M5c 1p1). When such software is employed, the target texture series can be obtained by supplying prescribed parameters to the software.
However, when prior art software of this type is employed, pictures in which the starting and ending of the texture series i.e. the texture pattern (mode) are not continuous for the player often result.
There was therefore room for improvement in the creation of repeating pictures in the field of conventional image processing. It is therefore yet a further specific object of the present invention to enable the compilation of a texture series of this type by image processing.
B6. In a prior art image processing device, there were scenes in which, in order to improve the dramatic effect of the reproduced image, slow reproduction was performed in which the reproduction speed of character action was slowed down. However, the benefits of such slow-reproduction performance were limited. Yet a further specific object of the present invention is therefore to provide means for image processing for games whereby the speed of reproduction can be varied in order to create a better dramatic effect.